He almost got away with his first rape, overpowering a 39-year-old teacher on a walking trail. But his second victim, a 30-year-old nurse, fought back, stabbing him in the right buttocks as he choked her.

Casey Hayslett Jr., now 17, hung his head and began to cry in a Shelby County courtroom Thursday while entering a guilty plea that requires him to serve a minimum of 16½ years in prison.

Criminal Court Judge Mark Ward told the teen, "You must be placed on the sex offender registry subject to community supervision for the rest of your life."

The teen later buried his face in his hand.

Both of his victims had been willing to testify, but only the nurse came to court. She decided not to address the judge or talk about her ordeal.

A year before the attacks, Hayslett was an athlete at Lowrance Elementary, a school that has classes from kindergarten to eighth grade, and had been voted "Most Popular" and "Most Attractive," with two photos of him smiling next to female classmates featured on the "Superlatives" page of the school's annual.

When he and a teacher came face-to-face while passing one another on a walking trail behind the school, he cordially nodded. But seconds later, he turned around and attacked the woman from behind, knocking her to the ground and raping her.

She called police, giving a description and undergoing a rape exam at the rape crisis center, where semen was collected. The teen had never been convicted of a sex crime so his DNA was not on file with a national database.

He may not have been caught had he not struck again, just three weeks later, said prosecutor Terre Fratesi.

Hayslett ran off, bleeding and holding his backside, which caught the attention of a neighbor who alerted police.

Within minutes, Shelby County Sheriff's deputies were at the teen's doorstep near the school.

Hayslett wiped some of his blood on a kitchen knife and claimed he accidentally cut himself while trying to cut off a loop from his pants.

But when first responders rushed to the nurse on the trail, she was still clutching her bloody knife. It had Hayslett's blood and flesh, which matched the DNA on file in the earlier incident.

Haylsett will serve 15 years — with no chance of early release — for the aggravated rape of the teacher. The judge ordered the 5-year sentence for attempted rape of the nurse to be served consecutively, or back-to-back, with state law requiring the youth to serve at least 30 percent.

"It's a significant sentence," Fratesi said after court. "There's no appeal. The victims are happy with it."